All-wheel drive (AWD) is a popular feature in modern cars, but it comes with a trade-off: reduced fuel efficiency. All things being equal, AWD vehicles tend to use more fuel than their two-wheel drive counterparts, which can result in higher fuel costs over time. But why is this? Well, the short answer is that AWD systems require more energy to operate, which means that more fuel is needed to power the vehicle. For the long answer we have gone into it in more detail below.
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What is AWD?
Before we dive into why all-wheel drive cars tend to chug down more fuel, let’s look at what it actually is. AWD is a drivetrain system that powers all four wheels of a vehicle, providing better traction and stability on various terrains. AWD is different from 4WD (Four-Wheel Drive) in that it is always on and does not require the driver to engage it manually.
How Does AWD Work?
AWD drivetrains use a combination of differentials, gears, sensors, and now software to detect when a wheel is slipping or losing traction. When this happens, the All-wheel drive system automatically sends power to the other wheels that have better traction, helping the vehicle maintain stability and control on various terrains.
Some AWD systems are designed to send power to the front or rear wheels only when necessary, while others distribute power to all four wheels all the time. Additionally, many all-wheel drive systems have an uneven split between the front and rear axles, and this can often be changed by selecting a different driving mode. For example, the Toyota GR Yaris features a 60/40 front/rear split in standard mode, but sport mode has a 30/70 split, and track mode has a 50/50 split. These different modes impact traction, fuel efficiency and more.
Factors that Affect Fuel Consumption
One of the main factors that contribute to the increased fuel consumption of AWD vehicles is the added weight of the AWD system. Cars with an all-wheel drive system need extra components that all add up to a surprising amount of weight. This added weight requires more energy to move, which in turn increases fuel consumption.
Another factor that impacts fuel consumption in AWD cars is the increased friction and losses in the drivetrain. This loss of efficiency in the drivetrain due to friction has been massively improved over the years with modern manufacturing techniques and designs, but it is still a factor that contributes to the increased fuel usage of AWD systems.
AWD vs. 2WD Fuel Efficiency
Compared to 2WD vehicles, AWD vehicles typically have lower fuel efficiency. According to the Environmental Protection Agency (EPA), the fuel economy of AWD vehicles is, on average, 2-3 miles per gallon (mpg) lower than that of 2WD vehicles. However, it is important to note that this can vary depending on the make and model of the vehicle, as well as driving conditions and other factors.
AWD vs. 4WD Fuel Efficiency
When it comes to fuel efficiency, AWD vehicles are generally more efficient than four-wheel drive (4WD) vehicles. This is because 4WD vehicles are designed to provide power to all four wheels at all times, which can result in increased fuel consumption. In contrast, AWD systems are designed to provide power to all four wheels only when needed, which can help to reduce fuel consumption.
What Are the Benefits of an AWD System?
Improved traction is arguably the biggest benefit when it comes to all-wheel drive systems. When things get slippery an all-wheel drive system can help improve handling and keep the car on the road.
We only have to look at the world of rallying to see the benefits of AWD systems. When Audi introduced their all-wheel drive Quattro it quickly proved that driving four wheels was the way to go on difficult and loose rally stages. Other competitors soon introduced their own all-wheel drive models and today all cars in the World Rally Championship are all-wheel drive.
Another benefit of AWD is increased safety. By improving traction and handling, AWD can help reduce the risk of accidents. This is particularly true in areas with inclement weather or hazardous road conditions. AWD can also help reduce the risk of skidding or sliding, which can be particularly dangerous when driving at high speeds.
Ways to Improve AWD Fuel Efficiency
While AWD cars do use more fuel, there are several ways to improve AWD fuel efficiency (the following also applies to two-wheel drive cars as well):
Proper Tyre Inflation
One of the easiest and most effective ways to improve AWD fuel efficiency is to maintain proper tyre inflation. Underinflated tyres can decrease fuel efficiency by up to 3%, while overinflated tyres can decrease fuel efficiency by up to 1%. It is important to check tyre pressure regularly and inflate tyres to the manufacturer’s recommended pressure.
Regular Maintenance
Regular maintenance is crucial for optimizing AWD fuel efficiency. This includes regular oil changes, air filter replacements, and tune-ups. A dirty air filter can reduce fuel efficiency by up to 10%, while a poorly tuned engine can reduce fuel efficiency by up to 4%. Regular maintenance can also help identify and address any issues that may be negatively affecting fuel efficiency.
Driving Habits
How you drive also has a significant impact on fuel efficiency. Aggressive driving, including rapid acceleration and hard braking, can decrease fuel efficiency by up to around 30%.
Conclusion
Essentially, all-wheel drive cars use more fuel due to increased inefficiencies in the system, added weight and a few other factors. The difference between modern all-wheel drive and two-wheel drive cars isn’t as big as it used to be, but it is still there and probably always will be. However, all-wheel drive cars can actually be more fuel efficient in very low traction situations where a two-wheel drive vehicle just spends all its time spinning its wheels and not moving.
